1. Field
The present invention relates to a lithographic apparatus including a support constructed to hold a patterning device, to a lithographic apparatus including a substrate table constructed to hold a substrate, to such a support, to a device manufacturing method including transferring a pattern from a patterning device onto a substrate, and to a method to attach a patterning device to a support constructed to hold the patterning device.
2. Description of the Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
In the lithographic apparatus, the patterning device may be held by a support. Commonly, the support will be provided with a drive device (such as linear motors) to move the support, thereby moving the patterning device held by the support. In this way, a simple exchangeability of the patterning device may be provided. Thus, in order to transfer another pattern onto the substrate, the patterning device may be exchanged with another patterning device. Commonly, an attachment mechanism is provided to be able to attach the patterning device to the support. Such attachment mechanism may include a mechanical clamp, an underpressure or vacuum suction device, an electrostatic clamp, or any other suitable constructions. Thereby, a force (in general a substantially stationary force) is applied between the patterning device and the support to be able to hold the patterning device.
In order to obtain a higher production volume and to improve the performance of the lithographic apparatus, it is desirable to increase the processing speed of the lithographic apparatus. On the other hand, the performance of a lithographic process is improved by increasing the resolution of the imaged pattern. In order to be able to increase the processing speed, the patterning device and, consequently, the support are subjected to higher accelerations. In that way, the patterning device can be positioned and moved at a higher speed. As a consequence, however, the patterning device is subjected to higher forces because of the larger accelerations. On the other hand, a higher complexity of chip structures or other semiconductor structures generally result in a larger size of the patterning device. However, the resolution and accuracy of the projection of the pattern may be more difficult to achieve with the use of larger patterning devices. The increase in the size of the patterning device has a twofold consequence on the forces to which it is subjected. At first, the increasing mass thereof will (given a certain acceleration of the patterning device) increase a force thereon. Moreover, such a larger size of the patterning device will also result in larger displacements thereof, thus as a consequence further increasing accelerations of the patterning device, thus further increasing forces thereon.
As explained above, the lithographic apparatus commonly uses a clamping mechanism or other holding mechanism to hold the patterning device by the support. As explained above, an increase of speed of the patterning support will result in an increase of forces on the patterning device. Commonly, the patterning device and, thus, the support, are subjected to accelerations along one of more axes which substantially coincide with a surface of the patterning device, thereby making e.g. scanning, stepping or other movements. As a consequence, the patterning device is subjected to forces parallel to the surface of the patterning device (e.g. due to inertia of the patterning device) which may translate into a tendency of the patterning device to slip with respect to the support, thereby limiting an achievable acceleration and a maximum size and weight of the patterning device, thus limiting a performance of the lithographic apparatus in order to avoid such slippage.
It is noted that slippage of the patterning device is undesired, as a displacement of the patterning device with respect to the support would adversely affect an accuracy of a positioning of the pattern on the substrate, thereby deteriorating a performance of the lithographic apparatus. Further, it is noted that in this document the terms slip, slipping and slippage may be used, however, these terms are to be understood as referring to a same phenomenon.